Magnetic shape memory (MSM) alloys deform strongly when subjected to a variable magnetic field due to the principle of magnetic-field-induced strain (MFIS). MSM devices may rely on the deformation caused by the MFIS to perform particular functions (e.g., applying mechanical pressure, sealing a chamber, fluid pumping, other actuation functions, etc.).
Typical MSM devices will apply a magnetic field to an entire MSM element to produce the deformation. However, the extent to which an MSM element expands is limited. For example, the MFIS for a typical MSM device is about 6%. To illustrate, for a device with a 20 mm long MSM element, the stroke, or in other words, the amount by which the MSM element may be extended is about 1.2 mm. One potential problem associated with typical MSM devices is that for some applications, a required stroke may be longer than the MSM element alone can produce may be required.
Some MSM devices may rely on the deformation of a portion of an MSM element to pump fluids. Examples of such MSM devices are described further in U.S. patent application Ser. No. 14/493,674, filed on Sep. 23, 2014 and entitled “Electrically Driven Magnetic Shape Memory Apparatus and Method,” and in U.S. patent application Ser. No. 13/550,386, filed on Jul. 16, 2012 and entitled, “Actuation Method and Apparatus, Micropump, and PCR Enhancement Methods,” the contents of each of which are hereby incorporated by reference in their entireties. These devices may also be subject to the same stroke limitations. Other drawbacks of current MSM devices may exist.